Retractable core head



April 4, 1944. J. M. CAMP 2,345,699

RETRACTABLE CORE HEAD Filed April 20, 1942 2 Sheets-Sheet 1 11% 772. Gama/1 INVENTOR.

A TTORNE Y April 4, 1944. J. M. CAMP 2,345,699

EEEEEEEEEEEEEEEEE AD l mented Apr. 4, i944 RETRACTABLE CORE HEAD John M. Camp, Tulsa, Okla, assignor to Standard Oil Development Company, a corporation 01' Delaware Application April 20, 1942, Serial No. 439,666

2 Claims.

The present invention is directed to a core head designed for passage through a. drill string and ior latching to the drill string for taking cores.

It is an object of the present invention to design a wire line retractable core head.

A further object of the present invention is to design a retractable core head which optionally may be provided with cutters particularly suited for drilling either hard or soft formations.

Other objects and advantages may be seen from the description taken in conjunction with the drawings in which Fig. 1 is an elevation, partly in section, of a shoe suitable for attachment to the lower end of a drill string for receiving a retractable core head;

Fig. 2 is an elevation, partly in section, of the shoe shown in Fig. 1 with a retractable core head in position;

Fig. 3 is an elevation of the retractable core head before it is latched to the shoe; and

Fig. 4 is a section taken along line IV-IV of Fla. 2. a

Referring now specifically to the drawings, shoe member i l is attached by suitable means, such as welding, to the lower end of drill string 12. The lower portion of member H is provided with a plurality of longitudinal slots which divide the lower portion into a plurality of segments or fingers it. Each finger terminates in a point which preferably connects to the full sized section by arcuate surfaces N. The sides E5 of the fingers are wedge-shaped so that the slots defined by the fingers will receive and retain the blades supporting the core head, which are described in greater detail hereafter. The interior of memher it is provided with a ledge or shoulder It.

The retractable core head comprises a cylindrical member H to which are attached downward- 1y extending spring blades ill, with the lower end oi each spring blade attached to a suitable cut ter it. In the illustration cutter i9 is of the rotary type conventionally used for drilling through hard rock, but obviously other cutters, such as those of the drag typ may be secured to spring blades l8. Member H is provided with outwardly projecting shoulders 28 arranged to cooperate with ledge it of the shoe in order to limit the downward movement of the core head.

Spring blades iii are proportioned and arranged to loch in the slots defined by fingers E3 of the casing shoe. The sides of the lower portion of spring blades 88 are provided with V-shaped grooves 2 0. On the outer surfac of each spring blade it is an outwardly extending ledge or shoulder 22 arranged to rest against casing shoe II when the core head is in position.

In operation the casing shoe is attached to the lower end of the string of drill pipe and the pipe is lowered in the bore hole until the casing shoe is near the bottom of the hole. The core head will then be dropped through the drill string until the cutters extend beyond the drill collar. A suitable expanding tool will then be forced down the drill pipe and into the core head to expand spring blades l8 outwardly. The drill string is then lowered until the cutters rest on the bot tom of the hole. Weight is then put on the drill string which. in turn, forces the core head upwardly with respect to said shoe. With grooves 2! of the spring arms mating with the V-shaped extensions it of fingers N the relative movement between the core head and the casing shoe will terminate when shoulders 22 of the spring arm come in contact with the upper ends or the easing shoe slots. When the core head is in this position, the expanding tool may be removed and the coring begun.

In a similar manner the core head may be removed by forcing an extracting tool down the drill stem to push the core head downward so that the spring blades may be released and allowed to contract inwardly. The cutters may then be engaged so that they will be retained in this inward position as the core head is raised to the surface of the earth.

While I have disclosed a specific embodiment of the present invention, it will be apparent to the worker skilled in the art that various changes may be made without departing from the scope of the present invention. For example. instead of using a rotary cutter, other types, such as drag type cutters or cutters built up of segments of various abrasive materials, may be employed. It will also be obvious that various means of locking the spring arms to the drill collar may be employed. For example, the slots arranged to receive the grooved part of the spring arms may have tapering rather than parallel sides.

Having thus described and illustrated the present invention, what I claim is:

l. A device suitable for taking cores comprising, in combination, a shoe adapted to be secured to the end of a string of drill pipe and provided with a plurality of downwardly extending fingers, a core head adapted for slidable movement within said shoe comprising a cylindrical memher, a plurality of downwardly extending arms with their upper ends firmly attached to the cy iindrical member and their lower ends movable radially and biased inwardly, and a cutter secured. to the lower end or each arm, said fingers and arms being provided with mating, longitudinally extending lands and grooves arranged for releasable engagement and to lock said head to said shoe when engaged.

2. A device suitable for taking cores comprising, in combination. a shoe adapted to be secured to the end of a string of drill pipe and provided with a plurality of longitudinally grooved downwardly extending fingers, a core head adapted for siidable movement within said shoe comprising a cylindrical member, a plurality of downwardly extending arms with their upper ends firmly attached to the cylindrical memher and their lower ends movable radially and biased inwardly, and a cutter secured to the lower end of each arm, said arms being providedwith longitudinally extending lands, said lands being arranged to engage releasably with the grooves 01 said fingers and to lock said head to said shoe 10 when engaged therewith.

JOHN M. CAIWP. 

